Effect of Different Concentrations of Propofol Used as a Sole Anesthetic on Pupillary Diameter: A Randomized Trial

Abstract

BACKGROUND: Pupillometry monitoring under general anesthesia is based on the assumption that pupillary diameter variations reflect the adequacy of the provided analgesia to the intensity of the nociceptive surgical stimulus. The accurate interpretation of pupillometric data requires establishing clearly what the expected baseline unstimulated pupillary diameter at each specific level of hypnosis is. Opioids decrease pupillary diameter in a dose-dependent fashion. In contrast, the effects of hypnotic drugs on pupillary diameter are not well known. Our aim was to describe the potential relationship between propofol predicted effect-site concentrations (Cets) ranging from 1 to 3 µg/mL and pupillary diameter. METHODS: Patients were randomized to receive propofol by target-controlled infusion at a predicted Cet of 1, 2, or 3 µg/mL (groups P1, P2, and P3, respectively). Pupillary diameter measurements were performed after 10 minutes of steady-state propofol infusion at the randomized Cet. No stimulation was performed during the study. Heart rate and bispectral index (BIS) were continuously recorded. RESULTS: Forty patients were included: (13, 14, and 13 in groups P1, P2, and P3, respectively). Mean pupillary diameter was 5.7 mm (1 mm) in group P1, 4.8 mm (1.3 mm) in group P2, and 3.3 mm (0.8 mm) in group P3. Propofol had a dose-dependent effect on pupillary diameter (linear regression R 2 = 0.45, P < .001). Pupillary diameter was positively correlated with the BIS (Spearman r = 0.75 [95% confidence interval (CI), 0.54 to −0.87] P < .001). CONCLUSIONS: From 1 to 3 µg/mL of predicted Cet, propofol has a dose-dependent effect on pupillary diameter. Within this concentrations range, there is a positive correlation between BIS and pupillary diameter. The subcortical effect of propofol on pupillary diameter is correlated to its effect on the cortex. Studies assessing pupillary diameter as a marker of the nociception–antinociception balance should be performed in patients with a standardized depth of hypnosis.

Dexmedetomidine and Other Analgosedatives Alter Pupil Characteristics in Critically Ill Patients

“…Despite anecdotal assumptions that most analgosedatives decrease both pupil reactivity and size (7)(8)(9)(10)34), our work is consistent with Larson and Talke (12) finding that dexmedetomidine is associated with increased pupil reactivity. One hypothesized mechanism is that dexmedetomidine, an α2 agonist, activates autoreceptors in the locus coeruleus and disinhibits the EWNmediated pupillary constriction (31,35).…”

“…However, the number of patients who received propofol ( N = 106) and fentanyl ( N = 68) was higher, and an absence in reactivity change was also supported by the work by Shirozu et al (10) and Kim et al (19). Smaller pupil size following propofol, fentanyl, and midazolam administration supports published findings in both healthy and anesthetized patients (Supplementary Table 3, http://links.lww.com/CCX/A987) (7–9).…”

“…There is conflicting evidence regarding the effect of IV infusion analgosedatives on pupil reactivity and size (6)(7)(8)(9)(10). Case series suggest that α2 agonists, such as dexmedetomidine and clonidine, may cause a paradoxical increase in reactivity (11)(12)(13)(14).…”

Pupil Diameter Changes after Anesthesia with Different Doses of Sufentanil under Ultrasound Monitoring

“…The main effect of propofol is to induce unconsciousness through inhibiting neurotransmission in the cerebral cortex, and there are also many subcortical effects. Propofol works on the PD through the subcortical structure (midbrain) [ 11 ]. The effect of propofol on pupil contraction is dose-dependent.…”

Pseudophakic Angle Closure Due to Vitreous Block Following Ureteroscopic Lithotripsy

“…4 Both intubation and extubation can trigger the gag reflex and severe coughing, which increase intrathoracic pressure and IOP. 5 Some types of anesthetic agents and depths of anesthesia may also interfere with pupillary size, 6 thereby facilitating iris-vitreous blockage. Furthermore, in some stages of anesthesia, a mydriatic pupil may allow the vitreous to move from the posterior segment to the pupillary plane, which results in vitreous block during return to the normal pupillary size condition.…”